ShareDataWithVF_Component.xml

<aura:component implements="force:appHostable,flexipage:availableForAllPageTypes" access="global" >
    <aura:attribute name="message" type="String"/>
    <aura:attribute name="visualforceDomain" type="String"
                    default="manish-winter19-dev-ed--c.visualforce.com"/>
    
    <aura:handler name="init" value="{!this}" action="{!c.doInit}" />
    
    <lightning:card title="Post Message Demo">
        <lightning:layout multipleRows="true">
            <lightning:layoutItem padding="around-large">
                <lightning:input type="text" label="Message:" value="{!v.message}" class="lightning-input"
                                 variant="label-hidden" placeholder="Type your messsage here..."/>
            </lightning:layoutItem>
            <lightning:layoutItem padding="around-large">
                <lightning:button label="Send to VF" onclick="{!c.sendToVF}"/>
            </lightning:layoutItem>
            <lightning:layoutItem size="12" padding="around-large">
                <span id="allMessages"/>
            </lightning:layoutItem>
        </lightning:layout>
        
        <lightning:layout>
            <lightning:layoutItem size="12">
                <!-- The Visualforce page to send data to -->
		<lightning:card title="I am a Visualforce Page inside Lightning Component" class="vf-card">
                    <iframe aura:id="vfFrame"  frameborder="0" width="100%" height="200" 
                            src="{!'https://' + v.visualforceDomain + '/apex/ShareDataWithLightning_VF'}"/>
                </lightning:card>
            </lightning:layoutItem>
        </lightning:layout>
    </lightning:card>
    
    
</aura:component>